Because the plan is to never have excess or idle workers. I used taxis as the example, I could’ve used elderly care where things are run similar to what you suggest. Well, 80% of its is run by public nurses while the other 20% is run by private companies. The issue is sort of similar, the small companies go bankrupt and then the public side needs to cover for them, but you don’t have staff to just scale up and run another 3% without using subs, which are often 3-10x expensive than on staff nurses.

You and I can agree that it’s sort of silly. The data will certainly show the net benefit of having idle workers, but you’re not going to win an election by wanting to have “too many” workers, even if the data shows that it is in fact not “too many”.